The present invention relates to health care accessories and, in particular, it concerns methods and devices for reducing trembling of the limbs such as is commonly experienced by sufferers of Parkinson""s disease or the like.
A significant proportion of the population suffer from trembling or shaking, referred to technically as xe2x80x9ctremorxe2x80x9d. Tremor is a common medical symptom consisting of a rhythmic oscillation of a part of the body around a fixed point. Tremors most often involve the distal parts of limbs, although they can also affect the head, tongue, jaw, or rarely the trunk. The mechanisms by which tremors are generated have been poorly understood. It is long been thought, however, that tremors are brought about by interactions of nerve cells in complex, incompletely understood circuits within the brain.
Tremors are subdivided clinically in a number of ways according to distribution, frequency, amplitude, and/or relationship to volitional movement. One type of tremor that is commonly recognized is known as tremor at rest. This is a coarse tremor with an average rate of 4 to 5 beats per second and is a frequent feature of Parkinson""s disease. This type of tremor gains its name from its relationship to volitional movement. This tremor typically occurs when a limb is at rest; willed movement temporarily suppresses the tremor. In some cases, the tremor is constant; in others it varies from time to time and may extend from one group of muscles to another as the disease progresses.
Another type of tremor, termed action tremor or intention tremor, is associated with cerebellar disorders. For example, patients with multiple sclerosis, which frequently involves the cerebellum and its connections, sometimes develop a coarse tremor which is brought on by activity and absent at rest. Other cerebellar disorders, such as the inherited cerebellar degenerations, also may have action tremor as a major symptom.
Another, tremor brought out by activity is known as essential (or essential-familial) tremor. This tremor sometimes begins in childhood but usually occurs later and persists through adult life, often affecting several members of a family (hence its name). It is known that essential-familial tremors can be suppressed by primidone or CNS-active xcex2-adrenergic blocking agents, such as propranolol.
A number of other types of tremors also exist, including physiologic tremor (typically associated with excitement and other hyperandrenergic states; stage fright is a typical example). Numerous reviews of the various tremor states exist, such as can be found in Chapter 15 (entitled xe2x80x9cParalysis and Other Disorders of Movementxe2x80x9d) of Harrison""s Principles of Internal Medicine 11th Edition, Brownwald et al., Eds., McGraw-Hill Book Company, New York, 1987.
Unfortunately, many patients with tremor are resistant to current therapies. The tremor of patients with Parkinson""s disease may be only partially responsive to the actions of trihexyphenidyl and related anticholinergic drugs or to dopamine agonists. Additionally, unacceptable central nervous system side effects, including confusion and hallucinations, are sometimes associated with current Parkinson""s disease treatments. Treatments of the tremor of cerebellar disease are also generally ineffective.
In the absence of safe and effective treatments to cure or suppress the aforementioned trembling symptoms of all types, is would be highly advantageous to provide a device and corresponding method for reducing the amplitude of the trembling motion of a limb of a human subject. SUMMARY OF THE INVENTION
The present invention is a method and device for reducing trembling of a limb of a human subject.
According to the teachings of the present invention there is provided, a method for reducing an amplitude of a trembling motion of a part of a human limb in at least one direction and at at least one frequency, the method comprising suspending a mass from the limb via a suspension configuration, the suspension configuration having an effective spring constant and/or a non-zero coefficient of damping in the at least one direction such that the mass is driven to oscillate in the at least one direction out of phase relative to the trembling motion, thereby reducing the amplitude of the trembling motion.
There is also provided according to the teachings of the present invention, a device for reducing an amplitude of a trembling motion of a part of a human limb in at least one direction and at at least one frequency, the device comprising: (a) a mass; and (b) a suspension configuration configured for suspending ;the mass relative to the part of the limb, the suspension configuration being configured to provide a given effective spring constant and/or a non-zero coefficient of damping between the limb and the mass in the at least one direction such that, when attached to the part of the limb, the mass is driven to oscillate in the at least one direction out of phase relative to the trembling motion, thereby reducing the amplitude of the trembling motion.
There is also provided according to the teachings of the present invention, a method for reducing an amplitude of a trembling motion of a part of a human limb in at least one direction, the method comprising: (a) sensing motion of the limb in the at least one direction; and (b) generating a variable force in the at least one direction, the variable force being varied in such a manner as to reduce an amplitude of the trembling motion.
Finally, there is also provided according to the teachings of the present invention, a device for reducing an amplitude of a trembling motion of a part of a human limb in at least one direction, the device comprising: (a) a bracket for mounting substantially rigidly on the limb; (b) a motion sensor associated with he bracket and configured to produce an output indicative of motion of the limb in the at least one direction; (c) an actuator associated with the bracket and configured to selectively generate a force in the at least one direction; and (d) a control unit associated with both the motion sensor and the actuator, the control unit being responsive to the output to actuate the actuator in a manner such as to reduce an amplitude of the trembling motion.